In all types of excavation equipment, buckets having teeth along the front edge of the bucket are employed for digging, scraping, and shoveling earth and ore. Accordingly, the bucket teeth, which are spaced along the front edge of the bucket, are subject to wear and must be replaced. The front edge of the bucket between the teeth, the bottom of the bucket, the interior of the bucket, the sides and the corners of the bucket are also subject to wear. Usually, the bucket teeth, which are individually known as tooth points, are replaced when excessively worn. On the other hand, if a bucket bottom, sides or the like are worn down through wear, the bucket is replaced or repaired by welding plate metal to the worn area.
A tooth point is normally mounted to the bucket by coupling it to an adapter that is mounted to the bucket. In this way, each tooth is an assembly of a tooth point and an adapter. Accordingly, as the tooth point is worn down, the tooth point can be replaced without having to replace the adapter. Examples of tooth point and adapter assemblies for excavation bucket teeth are shown in U.S. Pat. Nos. 3,462,861; 3,621,594; 3,851,413; and 4,027,408. In addition, U.S. Pat. Nos. 3,621,594 and 3,851,413 disclose wear prevention shrouds that fit between the teeth to protect the front edge and adjacent top and bottom areas of the bucket from being worn.
The teeth must be securely fastened to the bucket. In this regard, the connection between each tooth point and adapter needs to be able to withstand the high stress placed on the connection during excavating operations. The extent of wear occurring to the tooth point and on the bucket is dependent upon the material being excavated. If the material being excavated is highly abrasive, then the wear to the tooth point and bucket will be excessive and the tooth point will have to be replaced more frequently than if the material being excavated is less abrasive. When the tooth points must be replaced frequently, a problem occurs wherein the manner of securely mounting the tooth point to the adapter or bucket prevents the tooth point from being easily replaced. For example, in U.S. Pat. No. 3,462,861, the tooth point is mounted to the adapter by an interfitting groove and projection along an upper portion of the adapter and a shim driven between the tooth point and adapter along the lower portion of the adapter. Accordingly, when the tooth point needs to be replaced, the shim must be driven out of the tooth point cavity, which becomes difficult if the material being excavated has become packed in against the shim.
A similar difficulty occurs in replacing the adapters for the tooth points and for replacing other wear prevention elements such as bucket wear plates and shrouds. For example, in U.S. Pat. No. 3,621,594, the adapters are secured to the bucket by a fluted wedge and spool arrangement wherein the wedge is driven to lock the adapter to the bucket. In practice, it is common to weld the wedge and spool together in order to prevent relative movement between the pieces so the weld must be broken or cut before the adapter can be removed. In U.S. Pat. No. 3,621,594, the adapters, protectors and tooth points are secured by retaining pins that are removably secured by split spring rings located in counterbores. Therefore, it is necessary to remove the material that is packed into the counterbores from the excavating operation before the split spring ring and retaining pins can be removed and the protectors, tooth points and adapters replaced.
Although it is the practice to replace the adapters for the teeth if they become worn, this is unnecessary if the tooth points are replaced before they are worn through by the abrasive material being excavated. The degree of wear that has occurred for each tooth point is difficult to determine, however. Further, the pattern of wear that occurs is different for each type of material being excavated and the pattern also differs according to the way in which the equipment is being operated. The reason it is difficult to determine the extent of wear of a tooth point is that the tooth point is usually designed to completely enclose the adapter so that wear on the adapter is prevented. Also, full metal to metal contact is usually required in order that a secure mounting arrangement is provided between the tooth point and adapter. Accordingly, an estimate of the amount of metal that remains before the tooth point will be worn through to the adapter is difficult unless the operator is familiar with the adapter shape and its relation to the tooth point in view of the extent of wear that has occurred to the tooth point at the time of inspection.
In view of the difficulties encountered in securely mounting wear prevention elements to the bucket of an excavation apparatus, little attention has been paid to protecting the interior of the bucket from being exposed to abrasion and wear and to preventing the broad flat bottom exterior portion of the bucket from being worn through. Of course, the extent of wear to these parts of the bucket is also smaller in relation to the wear that occurs at the lip of the bucket and this has contributed to the lack of consideration to preventing wear from occurring to these parts. Ordinarily, should a bucket wear problem occur along the bottom of the bucket or within the interior of the bucket, a patch is applied to the worn area by welding plate steel to the worn surface. Of course, this requires the availability of the plate metal for the patch and an experienced welder to perform the repair. Further, should the repair be needed on a curved portion of the bucket, an appropriately curved patch of plate steel needs to be fabricated in order to satisfactorily complete the patch. As excavating apparatus are ordinarily maintained in continuous use in the field, this type of patch work is difficult to perform unless the apparatus is hauled to an appropriate repair facility, which requires that the apparatus be taken out of service.